The present invention pertains to carrying devices. More particularly, the present invention pertains to an improvement in carrying devices for lifting and carrying sheets of material.
Construction material, such as sheet-rock, plywood, or paneling, typically comes in large sheets. Moving the sheets around the construction site or from the place of purchase is a very difficult operation, especially for a single individual. This is primarily due to the awkwardness of the large sheets of material due to their size and the inability of an individual to adequately grasp and maneuver the sheet. Oftentimes, because of the awkwardness of maneuvering large sheets of material, the sheets will be damaged by being dropped or bumped into other objects. In particular, due to the fragile nature of sheet-rock, oftentimes the corners or edges of a sheet of sheet-rock material is damaged due to mishandling primarily caused by the awkwardness of handling a large sheet. This results in the sheet of sheet-rock being unusable as a full sheet.
U.S. Pat. No. 4,013,202, issued to Russo, teaches a device for conveniently lifting and transporting a large sheet of material. Referring to FIG. 6, the prior art sheet carrying device 1 taught by Russo includes a substantially U-shaped frame 2. This substantially U-shaped frame 2 has parallel arms 4 and 6 and bent arms 8 and 10. Bent arms 8 and 10 are bent at an angle to a plane defined by arms 4 and 6 so as to position a crossbar 12 having a finger clearance from the surface of a sheet S when the sheet S is being gripped in this prior art device 1. The prior art sheet carrying device 1 includes side arms 14 and 16 which have a crossbar 18 disposed therebetween. Mounting arms are provided which have cams 20 and 22 rotatably supported therefrom. These cams are pivotally supported by the mounting arms adjacent to the plane formed by parallel arms 4 and 6. These cams 20 and 22 are mounted eccentrically and arranged to be rotated into a tighter gripping engagement with a sheet of material placed against the plane by the gravitational forces exerted upon the sheet as the frame is lifted. These cams are also joined for common movement by a connecting rod 24.
A worker W can lift the sheet S by holding onto the lower crossbar 12 with one hand and the upper crossbar 18 with the other. The upper crossbar 18 will rest against the shoulder of the user W. This prior art device does not provide any means for preventing the upper crossbar 18 from sliding on the shoulder, which results in difficulty of maneuvering of the sheet S.
Also, the lower crossbar 12 contacts with the user's leg when walking making walking with the sheet of material held by the prior art device 1 difficult. Also, this prior art device 1 does not provide any way to alter the length between the top crossbar 18 and the bottom crossbar 12 to accommodate workers of different heights. Furthermore, this prior art device 1 does not provide any means for adequately gripping a sheet of material having a smooth surface. Instead, the sheet is gripped between the cam 20 and 22 and the parallel arms 4 and 6 respectively.
Furthermore, the surface contact area between the cams 20 and 22 and the sheet of material is relatively small creating areas of localized compression stress where the cams contact with the sheet S. Additionally, this prior art sheet carrying device 1 requires that the worker W control and support the sheet substantially only using his arms, with the upper crossbar 18 balanced on his shoulder.